Hydrogen gas generator and hydrogen gas generation method

Abstract

The objective is to provide a hydrogen gas generator and a hydrogen gas generation method that can produce clean hydrogen at low cost. [Solution] The hydrogen gas generator 10 comprises a supply pipe 12 for supplying raw materials M for hydrogen gas generation, with one end 12a protruding above ground and the other end 12b reaching a geothermal storage layer underground, and a recovery pipe 14 for recovering the generated hydrogen gas, with one end 14a protruding above ground and the other end 14b reaching a geothermal storage layer. The supply pipe 12 penetrates the side wall of the recovery pipe 14 at a penetration portion 18, and is located inside the recovery pipe 14 from the penetration portion 18 to the other end 12b. The raw materials M are characterized by containing iron and water.

Description

Technical Field

[0001] The present invention relates to a hydrogen gas generator and a hydrogen gas generation method.

Background Art

[0002] In recent years, hydrogen has attracted attention as a clean energy that does not emit carbon dioxide, and its application to fuel cell vehicles and the like has been studied.

[0003] As a technology related to the present invention, for example, in Patent Document 1, there are steps of circulating alcohol and water using a pipe, pressurizing the alcohol and water in the pipe in a mixed state using the self-weights of the flowing alcohol and water, and heating the mixture through the pipe by an external heat source, thereby forming a region of a mixture containing supercritical water or subcritical water in at least a part of the pipe, a step of generating hydrogen gas from the mixture in the formed region, and a step of recovering the generated hydrogen gas through the pipe. A hydrogen gas production method is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technology disclosed in Patent Document 1 is to inject a mixture of alcohol and water as a raw material deep into the ground and decompose the alcohol with water in a supercritical state using clean energy such as geothermal energy to generate hydrogen gas. There is a possibility that carbon dioxide or carbon monoxide may be generated when decomposing alcohol. In addition, since it takes an enormous cost to implement the hydrogen gas production method disclosed in Patent Document 1 and the like, it is difficult to put it into practical use.

[0006] The object of the present invention is to provide a hydrogen gas generator and a hydrogen gas generator that can produce clean hydrogen at low cost. [Means for solving the problem]

[0007] The hydrogen gas generating apparatus according to the present invention comprises a supply pipe for supplying raw materials for hydrogen gas generation, with one end protruding above ground and the other end reaching a geothermal storage layer underground, and a recovery pipe for recovering the generated hydrogen gas, with one end protruding above ground and the other end reaching the geothermal storage layer, wherein the supply pipe penetrates the side wall of the recovery pipe at a penetration point and is located inside the recovery pipe from the penetration point to the other end, and the raw materials contain iron and water.

[0008] Furthermore, in the hydrogen gas generating apparatus according to the present invention, it is preferable that the tip of the other end of the supply pipe has a slit.

[0009] Furthermore, in the hydrogen gas generating apparatus according to the present invention, the raw material is preferably a slurry-like mixture containing iron powder and water.

[0010] The hydrogen gas generation method according to the present invention comprises the steps of supplying raw materials for hydrogen gas generation to a geothermal reservoir underground, reacting the raw materials in the geothermal reservoir to generate hydrogen gas, and raising the generated hydrogen gas to the surface for collection, wherein the raw materials include iron and water.

[0011] Furthermore, the hydrogen gas generation method according to the present invention preferably further includes a step of mixing iron powder and water to produce a slurry-like mixture which is the raw material. [Effects of the Invention]

[0012] According to the present invention, clean hydrogen can be produced at low cost. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows a hydrogen gas generator according to an embodiment of the present invention. [Figure 2] This is an enlarged view of the other end of the supply pipe and the recovery pipe in a hydrogen gas generator according to an embodiment of the present invention. [Figure 3] This flowchart shows the procedure for generating hydrogen in a hydrogen gas generation method according to an embodiment of the present invention. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following, the same reference numerals will be used for similar elements in all drawings, and redundant explanations will be omitted. In addition, in the descriptions within the text, reference numerals previously mentioned will be used as necessary.

[0015] Figure 1 shows a hydrogen gas generator 10 according to an embodiment of the present invention. Figure 2 is an enlarged view of the other end of the supply pipe 12 and the recovery pipe 14 in the hydrogen gas generator 10 according to an embodiment of the present invention.

[0016] Figure 3 is a flowchart showing the procedure for generating hydrogen in the hydrogen gas generation method according to an embodiment of the present invention.

[0017] The hydrogen gas generator 10 includes a supply pipe 12 for supplying raw material M for hydrogen gas generation and a recovery pipe 14 for recovering the generated hydrogen gas.

[0018] The supply pipe 12 has one end 12a protruding above ground and the other end 12b reaching the underground geothermal reservoir 20. The one end 12a of the supply pipe 12 is the inlet for the raw material M. The raw material M introduced from the one end 12a falls by its own weight, passes through the other end 12b, and is supplied to the geothermal reservoir 20. The supply pipe 12 is, for example, a steel pipe.

[0019] The geothermal reservoir 20 is a permeable rock layer existing at a depth of several hundred to several thousand meters underground, and is a region where high-temperature geothermal fluid (hot water or steam) is stored or circulated. The geothermal reservoir 20 is composed of volcanic rocks (such as andesite and rhyolite) containing many fractures and fault structures, and is heated by magma heat supplied from underground. In addition, the geothermal reservoir 20 is covered by a relatively impermeable caprock layer (such as tuff and mudstone) around it, forming a structure to prevent heat and fluid from escaping to the outside.

[0020] In this specification, the geothermal reservoir 20 is located at a depth of about 1,000 to 4,000 m and has a high-temperature and high-pressure environment (temperature T≧374℃, pressure P≧22.1MPa) in which water becomes supercritical.

[0021] The raw material M contains iron and water. In the geothermal reservoir 20, the water in the raw material M becomes supercritical (hereinafter, supercritical water is referred to as supercritical water). Supercritical water has the characteristics of having both the properties of a liquid and a gas and being highly reactive. The iron is, for example, iron powder.

[0022] Generally, under strong acidic conditions of about pH 1 to 3, iron and hydrogen ions in water react as follows to generate hydrogen gas together with iron ions. Fe+2H + →Fe 2+ +H 2 ↑···Reaction formula (1)

[0023] In addition to the above reaction formula (1), iron and water react as follows to generate hydrogen gas together with iron oxide. 3Fe+4H2O→Fe3O4+4H2↑···Reaction formula (2)

[0024] The reaction of reaction formula (2) can occur not only under strong acidic conditions of about pH 1 to 3 as in reaction formula (1), but also under weak acidic conditions to neutral conditions. However, when ordinary water is used, the reaction rate is very slow and hydrogen gas is not substantially generated.

[0025] Because supercritical water has a much higher reactivity (oxidizing power) compared to ordinary water, the reaction in reaction equation (2) above proceeds particularly efficiently when iron and supercritical water are present together, and the hydrogen production efficiency is greatly improved. In other words, by supplying raw material M containing iron and water to the geothermal reservoir 20, a large amount of hydrogen can be efficiently generated.

[0026] Both reaction equations (1) and (2) above do not produce carbon dioxide and can generate clean hydrogen. Furthermore, iron is relatively inexpensive compared to other metals such as magnesium and aluminum.

[0027] The temperature of the geothermal reservoir 20 is not particularly limited as long as the conditions for the water to reach a supercritical state are met, but it may be between 400 and 700°C, preferably between 400 and 600°C, and more preferably between 500 and 600°C. If the temperature of the geothermal reservoir 20 exceeds 700°C, the oxide film may stabilize and the reaction efficiency may decrease.

[0028] The raw material M is preferably a slurry-like mixture containing iron powder and water. If the iron powder and water are separated and introduced from one end 12a, the iron powder may adhere to the inside of the supply pipe 12 and not reach the other end 12b. By introducing the raw material M from one end 12a in a slurry-like state to ensure fluidity, the raw material M can be reliably introduced to the other end 12b.

[0029] The mixing ratio of iron to water in raw material M may be calculated stoichiometrically from reaction equation (2). By adjusting the mixing ratio of iron to water, the reaction rate and the amount of hydrogen produced can be adjusted. The amount of water may also be increased relative to the stoichiometrically calculated mixing ratio of iron to water. This allows the reaction to proceed more slowly and reduces the amount of unreacted iron.

[0030] The recovery pipe 14 has one end 14a protruding above ground and the other end 14b reaching the underground geothermal storage layer 20. Hydrogen gas generated by the supply of raw material M enters the recovery pipe 14 from the other end 14b, rises naturally within the recovery pipe 14, and reaches the one end 14a. Because hydrogen gas has a lower specific gravity than air, it does not require external energy and exhibits behavior of naturally floating and self-ejecting. Here, "self-ejecting" means the phenomenon in which hydrogen gas generated in the geothermal storage layer 20 rises naturally within the recovery pipe and is ejected to the ground due to its lightness and pressure difference, without the use of external power such as a pump.

[0031] One end 14a of the recovery pipe 14 is connected to a valve 16, and the naturally rising hydrogen gas is recovered from the recovery port 17 after its pressure and volume are adjusted by the valve 16.

[0032] The recovery pipe 14 may be newly constructed by excavating underground and burying a steel pipe or the like, but it is preferable to utilize an existing borehole such as a production well. This allows for the recovery of hydrogen gas at a low cost.

[0033] A production well has, for example, a well casing drilled down to a geothermal reservoir 20 and is configured to deliver high-temperature, high-pressure geothermal fluid (e.g., a multiphase fluid of 200-300°C) from the geothermal reservoir 20 to the surface. The production well has, for example, a steel casing pipe with a liner pipe on its inner circumference, and the area around the well casing is sealed with cement material to prevent groundwater contamination and collapse of the geological formation.

[0034] The supply pipe 12 penetrates the side wall of the recovery pipe 14 at a penetration section 18, and is positioned inside the recovery pipe 14 from the penetration section 18 to the other end 12b. This eliminates the need to excavate a new borehole for burying the supply pipe 12, and allows the other end 12b of the supply pipe 12 to reach the geothermal storage layer 20 by passing through the inside of the recovery pipe 14.

[0035] The other end 12b of the supply pipe 12 may protrude downward below the other end 14b of the recovery pipe 14. This suppresses interference caused by the rising airflow of hydrogen gas recovered from the other end 14b, thereby enabling a stable supply of raw material M to the geothermal reservoir 20.

[0036] The tip portion 12c on the other end 12b side of the supply pipe 12 preferably has a slit 30 (see Figure 2). This can further improve the hydrogen recovery efficiency. In the example shown in Figure 2, rectangular slits 30 with rounded corners are arranged at equal intervals such that the longitudinal direction of the slits 30 is approximately parallel to the longitudinal direction of the recovery pipe 14. However, the length, number, shape, etc. of the slits 30 are not particularly limited to the example in Figure 2, as long as the rigidity of the tip portion 12c is maintained. The hydrogen gas recovered from the other end 12b and the slits 30 rises through the space between the outer wall of the supply pipe 12 and the inner wall of the recovery pipe 14.

[0037] Next, the method for generating hydrogen gas according to the present invention will be described (see Figure 3).

[0038] First, iron powder and water are mixed to create a slurry-like mixture, which is used as the raw material M for hydrogen gas generation (S1). Although step S1 may be omitted and iron powder and water may be supplied individually in step S2 described later, supplying the iron powder and water simultaneously in a slurry form ensures that the raw material M reaches the geothermal reservoir 20.

[0039] The prepared raw material M is supplied to the geothermal reservoir 20 (S2), and hydrogen gas is generated by reacting the raw material M in the geothermal reservoir 20 (S3). Specifically, in step S2, a supply pipe 12 is used, with one end protruding above ground and the other end reaching the underground geothermal reservoir, and the raw material M is allowed to fall naturally from the ground to the geothermal reservoir 20 within the supply pipe 12. In step S3, the water in the geothermal reservoir 20 is transformed into supercritical water in a supercritical state, and hydrogen gas is generated when the supercritical water oxidizes iron.

[0040] The generated hydrogen gas is allowed to rise and is recovered on the ground (S4), and the hydrogen gas generation method according to the present invention is completed. Specifically, in step S4, a recovery pipe 14 is used, with one end protruding above ground and the other end reaching the underground geothermal reservoir, and the hydrogen gas is allowed to rise naturally from the geothermal reservoir 20 to the ground within the recovery pipe 14.

[0041] As described above, the hydrogen gas generator or hydrogen gas generation method according to the present invention utilizes natural underground conditions and eliminates the need for large-scale external energy supply, enabling the low-cost and clean production of hydrogen gas. Furthermore, in this invention, since the supercritical fluid present in the geothermal reservoir can be recovered without passing through the supply pipe and recovery pipe, the deterioration of equipment used for hydrogen gas recovery, such as the supply pipe and recovery pipe, can be suppressed compared to production wells that recover supercritical fluid from highly acidic geothermal sources. [Explanation of symbols]

[0042] 10 Hydrogen gas generator, 12 Supply pipe, 12a one end, 12b the other end, 12c tip, 14 Recovery pipe, 14a one end, 14b the other end, 16 Valve, 17 Recovery port, 18 Penetration section, 20 Geothermal storage layer, 30 Slit.

Claims

1. A supply pipe for supplying raw materials for hydrogen gas generation, with one end protruding above ground and the other end reaching the underground geothermal reservoir, A recovery pipe for recovering generated hydrogen gas, with one end protruding above ground and the other end reaching the geothermal reservoir, Equipped with, The supply pipe penetrates the side wall of the recovery pipe at the penetration point, and is positioned inside the recovery pipe from the penetration point to the other end. The hydrogen gas generator is characterized in that the raw materials include iron and water.

2. In the hydrogen gas generator according to claim 1, A hydrogen gas generating apparatus characterized in that the tip of the other end of the supply pipe has a slit.

3. In the hydrogen gas generator according to claim 1, The hydrogen gas generating apparatus is characterized in that the raw material is a slurry-like mixture containing iron powder and water.

4. The process involves supplying raw materials for hydrogen gas generation to a geothermal reservoir underground, The steps include: reacting the raw materials in the geothermal reservoir to generate hydrogen gas; The steps include raising the generated hydrogen gas to the ground and recovering it, Includes, A method for producing hydrogen gas, characterized in that the raw materials include iron and water.

5. In the hydrogen gas generation method according to claim 4, A method for producing hydrogen gas, further comprising the step of mixing iron powder and water to produce a slurry-like mixture which is the raw material.

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